Electric pickup for vibrations



y 1951 L. A. MAAS ELECTRIC PICKUP FOR vxsmnous Filed April 22, 1949INVENTOR. 400/54 M445 47'7'0R/VEK Patented May 22, 1951 ELECTRIC PICKUPFOR VIBRATIONS Louis A. Maas, Glendale, Calih, assignor to Maas- RoweElectromusic Corporation, Los Angeles, Calif a corporation of CaliforniaApplication April 22, 1949, Serial No. 88,980

10 Claims.

This invention relates to the conversion of mechanical vibrations intoelectrical impulses, and especially by the aid of a capacitance which isvaried in accordance with the vibrations. Such devices are useful, forexample, to translate the Vibrations of a vibrant bar or chime intoelectrical impulses that may be readily amplified and then convertedinto sound at a place remote from the vibrant bar or chime.

Pick-ups of this general character are especially useful for electricalmusical instruments of the percussion type. However, such pick-ups havebeen somewhat complex, and required quite delicate adjustments.

It is one of the objects of this invention to improve pick-ups of thisgeneral character.

It is another object of this invention to simplify such pick-ups and tomake it possible to adjust them expeditiously for optimum effects.

This invention possesses may other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This form is shown in the drawingsaccompanying and forming part of the present specification. It will nowbe described in detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense, since thescope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is an elevation of a vibrant bar utilizing the invention, thebar being shortened in order to reduce the size of the figure;

Fig. 2 is an enlarged fragmentary View of the bar, illustrating theinvention;

Fig. 3 is an enlarged sectional view, taken along a plane correspondingto line 33 of Fig. 2; and

Fig. 4 is a pictorial view of one of the leaf springs used in connectionwith the invention.

In the present instance, a vibrant bar i is shown which may be in theform of a hollow tube freely suspended at its upper end, as by the aidof a flexible cord 2. In order to producemusical vibrations of the bari, use is made of a striker mechanism 3, including anelectromagnetically operated striker 4 and a control switch 5.

The vibrations of the vibrant bar i are intended to be electricallyamplified by an amplifier system 6 which ultimately passes energy toloud speaker I which converts electrical im pulses into sound waves.

In order that the mechanical vibrations of the bar I be translated intoelectrical impulses fed into the amplifier system 3, a capacitance is 3provided which is caused to vary in accordance with the mechanicalvibrations. One plate of a capacitor for this purpose is formed by thebar I, which is made of conducting material. An electrical connection 8connects the bar I to the amplifier system 6.

The other plate of the condenser is formed by an arcuate plate 9, whichis beveled, as indicated at H], at its upper and lower edges. This plate9 is connected, as by connection ii, to the amplifier system. Thus, theconductors 8 and l i may be coupled in any desired manner to the inputof the amplifier system 6.

As shown most clearly in Figs. 2 and 3, interposed between the bar 6 andthe plate A is a layer of dielectric material 52. This may be thin,cellulose material, the thickness of which is exaggerated in Fig. 3.Furthermore, the arcuate plate 9 is so arranged that it has a limitedarea of contact with the dielectric material 52. This may beaccomplished, for example, by making the plate 9 of slightly smallerradius than that of the tube i, so that the side edges it and N form theonly places of contact between the plate 9 and the dielectric material12.

The arrangement is such that the mechanical vibrations of the bar iserve minutely to vibrate the plate 9 with relation to bar i, therebycausing variations or oscillations in the capacitance of the condensedformed by the bar I and the plate 9. Thus, variations in capacitancecorrespond to the mechanical vibrations and, ac-

cordingly, affect the amplifier system 6.

In order that the plate 9 correspond in a desired manner to thevibrations, the location of the plate 9 along the length of the bar I ischosen so as to be properly affected by the compleX vibrations set up inthe bar I by the striker mechanism 3.

The plate 5; is resiliently urged toward seated position by the aid of apair oi leaf spring members l5 and it. Each of these leaf spring members has a rounded end i? engaging within a shallow groove formed in thearcuate resilient contacting or pad members it. These pad members is maybe made of rubber, or the like, and are in contact with the exteriorsurface of the plate These rubber members i8 are purposely made quitethick so that erratic vibrations 0% plate 3 are reduced.

The leaf springs iii are placed under stress, by the aid of thefastening means it, such as a screw, which are dreaded radially into thebar i and which pass through the clearance apertures 28 formed in theleaf springs l5. The ends 0. the leaf springs remote from the free endsii are bifurcated, as indicated at it in Fig. 4, to contact the exteriorsurface of the bar I. By adjusting the screw it the force exerted by thecorrespending leaf springs i5 and it may be varied to correspond to thedesired degree of response of the structure. Furthermore, each of theleaf springs 15 and to may be bent, as indicated at 22, so that the leafspring conforms generally to the corn tour of the tubular bar 1. Thebifurcated ends 2! thus serve as a fulcrum about which the correspondingleaf spring to or it can be moved by operation of the screws is.

Ihe forces transmitted by the leaf spring 55 to the chime bar l throughthe screw 2i} and the bifurcated end 2! of the leaf spring l5 are in aplane perpendicular to the line of vibration of the chime bar I. andhence have no restricting or damping effect on the bar. Other methods ofapplying pressure on the plate 9 generally have all or a portion ofthese forces transmitted to the chime in a direction parallel to theline of vibration of the chime, and hence have a tendency to oppose thevibration, causing the chime to up more rapidly.

Upon the occurrence of mechanical vibrations of the tube I, acorresponding movement between bar l and plate 9 is effected. Althoughthis movement is minute, it is yet sufficient to set up correspondingelectrical impulses in the input circult of the amplifier system 6.

The inventor claims:

1. In a pick-up structure: a vibrant electrica l conducting member; acooperating member forming a capacitance with the vibrant member; adielectric layer between the members; said dielectric layer being incontact with both said members; one of said members having a limitedarea of contact with said dielectric layer; and :1, pair of spring armseach attached to one of the members and having a free end overlying theother member for urging said other member to-- ward the one member, saidarms extending in such a direction that the forces exerted thereby leavethe resonant characteristics of the bar substantially unaffected.

2. In a pick-up structure: a vibrant electrically conducting member; acooperating member forming a capacitance with the vibrant member; adielectric layer between the members; said di electric layer being in.contact with both said members; and a pair of spring arms each attachedto one of the members and having a free end overlying the other memberfor urging said other member toward the one member, said arms extendingin such a direction that the forces e11- erted thereby leave theresonant characteristics of the bar substantially unaffected.

3. In a pick-up structure: a vibrant electrically conducting member; acooperating member form ing a capacitance with the vibrant member, adielectric layer between the members; said dielectric layer being incontact with both said members; a pair of spring arms for urging themembers together said arms extending in a pe ripheral direction aboutvibrant member, thereby leaving the resonant characteristics of the barsubstantially unaffected; and adjustable fastening means extendingrespectively through each arm and engaging one of the members.

4. In a pick up structure: a vibrant electrically conducting member; acooperating member form'- ing a capacitance with the vibrant member; adielectric layer between the members; said dielectric layer being incontact with both said members; a pair of spring arms for urging themembers together said arms extending in a peripheral direction aboutsaid vibrant member, thereby leaving the resonant characteristics of thebar substantially unaffected; and adjustable fastening means extendingres ectively through each arm and engaging one of the members; one ofsaid members having a limited area of contact with said dielectriclayer.

5. In a pick-up structure: an elongated vibrant electrically conductingmember; a cooperating member forming a capacitance wtih the vibrantmember; a dielectric layer between the members; said dielectric layerbeing in contact with both said members; a pair oi spring arms; eachspring arm having one end in contact with one of the members and itsother end overlying the other member for urging the members toward eachother said arms extending substantially perpendicularly of tlelongitudinal axis of said vibrant member, thereby leaving the resonantcharacteristics of the bar substantially liected; and a screw for eacharm, passing through an aperture in the arm and threaded into said oneof the members.

6. In a pick-up structure: a vibrant electrically conducting member; acooperating member forming a capacitance with the vibrant member; adielectric layer between the members; said dielectric layer being incontact with both said members; spring arms having a free end urging themembers together said arms extending in peripheral direction about saidvibrant member, thereby leaving the resonant characteristics of the barsubstantially unaiiected; and a resilient pad between the said end andone of the mem bore.

'7. In a pick-up structure: a vibrant electrically conducting member; acooperating member forming a capacitance wtih the vibrant member; adielectric layer between the members; said dielectric layer being incontact with both said members; one of said members having a limitedarea of contact with said dielectric layer; a pair of spring arms eachattached to one or" the members and having a free end overlying theother member for urging said other member toward the one member, saidarms extending in a peripheral direction about said vibrant member,thereby leaving the resonant characteristics of the bar substantiallyunaffected; and a resilient pad between each 01' the free ends and saidone member.

3. In a pick-up structure: an elongated vibrant bar made fromelectrically conducting material; a cooperating member forming acapacitance with the bar; a dielectric layer between the bar and themember and in contact with both of them; the member having a limitedarea of contact with said dielectric layer; and a pair of spring armsextending transversely to the bar and extending over the side edges ofthe member for urging the member toward the bar.

9. in a pick-up structure: an elongated vibrant bar made fromelectrically conducting material; a cooperating member for" ing acapacitance with tl e bar; a dielectric layer between the bar the memberand in contact with both of them; and means resiliently urging said barand member together, the force exerted by said means being substantiallyperpendicular to the line of vibration of the bar.

lo. In a pick-up structure: an elongated vibrant bar made fromelectrically conductin material; a cooperating member forming acapacitance with the bar; a dielectric layer between the bar and themember and in contact with both of them; a, pair of spring arms, eachhaving a free end extending over the side edges of said member forurging the member toward the bar; said arms extending perpendicularly ofthe longitudinal axis of said bar, thereby leaving the resonantcharacteristics of the bar substantially unafiected; and securing meansfor said arms adjustably controlling the force urging said member towardthe bar.

LOUIS A. MAAS.

REFERENCES CITED The following references are of record in the file ofthis patent:

5 UNITED STATES PATENTS Number Name Date 2,284,911 Maas June 2, 19422,362,797 Bokovay Nov. 14, 1944 2,413,062 Miessner Dec. 24, 1946 10

